This invention relates to a method of cultivating Basidiomycetes at high efficiency, while controlling occurence of excessive foaming, under aeration and agitation by using an aqueous liquid medium which produces vigorous foaming during cultivation of the fungi.
Generally, the aqueous liquid media of the type containing at least one substance selected from yeast extract, peptone, casamino acid and meat extract as a nutrient source (nitrogen source) and further containing a saccharide (such as glucose, starch, fructose, etc.) as a carbon source and an inorganic salt or salts (such as phosphate, magnesium salt, etc.) are suited for use in cultivation of Basidiomycetes. However, when a fungus of Basidiomycetes is subjected to submerged culture by using such an aqueous liquid medium, foaming occurs heavily at the surface of the liquid medium during cultivation and hence it proves extremely difficult to carry out cultivation efficiently and smoothly for a large quantity of medium in a fermentor. Therefore, when employing submerged culture of a fungus of the Basidiomycetes by using an aqueous liquid medium prone to foaming as described above, it is necessary to reduce the feed of the medium in the fermentor (to a level of approximately 40 to 60% of the capacity of the fermentor). However, since a considerable number of days are usually required for cultivation of the Basidiomycetes, such reduction of the medium feed leads to lowering of productivity.
Various devices have been employed, such as mounting a defoaming machine to the agitator in the fermentor, for controlling the foaming, but all of these devices are unsatisfactory in suppressing the foaming phenomenon of the medium to such an extent as makes it possible to increase the feed of the medium. It was also attempted to control foaming by reducing the rates of aeration and agitation in the medium, but this method is also undesirable as it lowers the rate of growth of the mycelia of the Basidiomycetes. It was further proposed to dilute the liquid medium to thereby suppress foaming and increase the medium charge, but this attempt is attended with the drawback that the yield of the mycelia per batch is intolerably reduced.